Communication systems typically include a plurality of communication devices, such as mobile or portable radio devices, that are geographically distributed among various base sites, and wirelessly communicate with the base sites and each other. To identify the presence of an incoming call from another communication device or a base site, communication devices are generally configured to detect the presence of one or more criteria, such as a synchronization signal. The communication device will not begin processing the call until such a criteria is received.
For example, in currently proposed standards for Association of Public-Safety Communication Officials (APCO) Project 25 Phase 2 Time Division Multiple Access (TDMA) systems, voice synchronization signals are transmitted once every 360 ms. If the initial voice synchronization signal in the call is not detected, 360 ms of voice information is lost, and voice information continues to be truncated until a voice synchronization signal is detected.
In the past, various system implementations have attempted to utilize fixed threshold levels for detection of the voice synchronization signal based on probabilities for detection and falsing. However, such fixed threshold levels result in various drawbacks depending on the selected level. For instance, while setting a lower threshold for detection of the voice synchronization signal may increase the probability of the receiving device detecting the voice synchronization signal, the lower threshold, however, may also increase the probability of the receiving device detecting and locking onto a false synchronization signal, thus decreasing the probability of the receiving device detecting the loss of the signal during the synchronization process. Similarly, while setting a higher threshold may decrease the probability of the receiving device detecting a false synchronization signal and may increase the probability of the receiving device detecting the loss of the signal during the synchronization process, the higher threshold, however, may also decrease the probability of the receiving device detecting the voice synchronization signal.
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